A large number of industrial sectors use or produce products that are supplied as heterogeneous liquid formulations, in which more than one phase exists. The properties and the added value of these disperse systems largely depends on their physico-chemical characteristics: the nature of the various phases present, degree of dispersion of one phase in the other, composition of the system, stability of the system over time, etc. The liposomes, emulsions and suspensions are important heterogeneous liquid formulations with a wide range of applications, e.g. additives and coatings, foodstuffs, drugs and cosmetics. In particular, liposomes are small spherical vesicle made up of a lipid bilayer that encloses an aqueous nucleus. Emulsions are systems made up of small drops of liquid dispersed in another liquid with which they are not miscible, and suspensions are systems formed by solid particles dispersed in a fluid.
Obtaining micro- and nanodisperse systems, such as micro- and nanoliposomes, micro- and nanoemulsions, micro- and nanosuspensions, would help increase the added value of end products in many industrial sectors, e.g. printing inks, cosmetics, powdered paints, drugs, coatings, etc. The obtaining of nanosuspensions of solid substances with high therapeutic activity but with low water solubility is of considerable interest to the pharmaceutical sector, since it would allow said substances to be administered intravenously or transdermally. It would also involve greatly increased stability of such disperse systems over time.
U.S. Pat. No. 5,145,684 uses the “pearl milling” technique for milling suspensions in water with surfactant in order to provide stable nanosuspensions.
U.S. Pat. No. 5,858,410 discloses a method of breakdown in suspension based on cavitation forces obtained at high pressure, using surfactants.
Application WO9965469 discloses a method in which a rapid expansion of a solution of the compound to be suspended is carried out in a supercritical fluid (RESS method) over an aqueous solution. Surfactants can be used in both the supercritical gas phase and the aqueous phase.
Application WO9714407 discloses a method related with the RESS method. In brief, it describes the preparation of disperse systems by depressurizing a solution of the compound to be suspended in a supercritical fluid without surfactant, carried out over water with surfactant.
Application WO02/09422A2 describes a method for obtaining nanosuspensions by precipitation from a solution, owing to the anti-solvent effect of the dispersant fluid (fluid E) on the latter.
At present, all the methods of preparation of micro- and nanodisperse systems are complex and consume large amounts of energy, since they either require many stages or they must be carried out at high pressure, such as pressures exceeding 100 bar. Thus exists considerable interest in research into and development and application of eco-efficient methods of obtaining micro- and nanodisperse systems.